diff --git a/lighthouse/tests/validator_client.rs b/lighthouse/tests/validator_client.rs
index 8c1f0477c4..27d7c10e96 100644
--- a/lighthouse/tests/validator_client.rs
+++ b/lighthouse/tests/validator_client.rs
@@ -499,3 +499,24 @@ fn latency_measurement_service() {
             assert!(!config.enable_latency_measurement_service);
         });
 }
+
+#[test]
+fn validator_registration_batch_size() {
+    CommandLineTest::new().run().with_config(|config| {
+        assert_eq!(config.validator_registration_batch_size, 500);
+    });
+    CommandLineTest::new()
+        .flag("validator-registration-batch-size", Some("100"))
+        .run()
+        .with_config(|config| {
+            assert_eq!(config.validator_registration_batch_size, 100);
+        });
+}
+
+#[test]
+#[should_panic]
+fn validator_registration_batch_size_zero_value() {
+    CommandLineTest::new()
+        .flag("validator-registration-batch-size", Some("0"))
+        .run();
+}
diff --git a/validator_client/src/cli.rs b/validator_client/src/cli.rs
index 6e199cb173..436b8eb4d5 100644
--- a/validator_client/src/cli.rs
+++ b/validator_client/src/cli.rs
@@ -333,6 +333,16 @@ pub fn cli_app<'a, 'b>() -> App<'a, 'b> {
                 .default_value("true")
                 .takes_value(true),
         )
+        .arg(
+            Arg::with_name("validator-registration-batch-size")
+                .long("validator-registration-batch-size")
+                .value_name("INTEGER")
+                .help("Defines the number of validators per \
+                    validator/register_validator request sent to the BN. This value \
+                    can be reduced to avoid timeouts from builders.")
+                .default_value("500")
+                .takes_value(true),
+        )
         /*
          * Experimental/development options.
          */
diff --git a/validator_client/src/config.rs b/validator_client/src/config.rs
index fa297dcfed..e0dd12e100 100644
--- a/validator_client/src/config.rs
+++ b/validator_client/src/config.rs
@@ -77,6 +77,8 @@ pub struct Config {
     pub disable_run_on_all: bool,
     /// Enables a service which attempts to measure latency between the VC and BNs.
     pub enable_latency_measurement_service: bool,
+    /// Defines the number of validators per `validator/register_validator` request sent to the BN.
+    pub validator_registration_batch_size: usize,
 }
 
 impl Default for Config {
@@ -117,6 +119,7 @@ impl Default for Config {
             gas_limit: None,
             disable_run_on_all: false,
             enable_latency_measurement_service: true,
+            validator_registration_batch_size: 500,
         }
     }
 }
@@ -380,6 +383,12 @@ impl Config {
         config.enable_latency_measurement_service =
             parse_optional(cli_args, "latency-measurement-service")?.unwrap_or(true);
 
+        config.validator_registration_batch_size =
+            parse_required(cli_args, "validator-registration-batch-size")?;
+        if config.validator_registration_batch_size == 0 {
+            return Err("validator-registration-batch-size cannot be 0".to_string());
+        }
+
         /*
          * Experimental
          */
diff --git a/validator_client/src/lib.rs b/validator_client/src/lib.rs
index 6e4a8da6ac..60943a260c 100644
--- a/validator_client/src/lib.rs
+++ b/validator_client/src/lib.rs
@@ -487,6 +487,7 @@ impl<T: EthSpec> ProductionValidatorClient<T> {
             .beacon_nodes(beacon_nodes.clone())
             .runtime_context(context.service_context("preparation".into()))
             .builder_registration_timestamp_override(config.builder_registration_timestamp_override)
+            .validator_registration_batch_size(config.validator_registration_batch_size)
             .build()?;
 
         let sync_committee_service = SyncCommitteeService::new(
diff --git a/validator_client/src/preparation_service.rs b/validator_client/src/preparation_service.rs
index 5bd93a5053..7d6e1744c8 100644
--- a/validator_client/src/preparation_service.rs
+++ b/validator_client/src/preparation_service.rs
@@ -23,9 +23,6 @@ const PROPOSER_PREPARATION_LOOKAHEAD_EPOCHS: u64 = 2;
 /// Number of epochs to wait before re-submitting validator registration.
 const EPOCHS_PER_VALIDATOR_REGISTRATION_SUBMISSION: u64 = 1;
 
-/// The number of validator registrations to include per request to the beacon node.
-const VALIDATOR_REGISTRATION_BATCH_SIZE: usize = 500;
-
 /// Builds an `PreparationService`.
 pub struct PreparationServiceBuilder<T: SlotClock + 'static, E: EthSpec> {
     validator_store: Option<Arc<ValidatorStore<T, E>>>,
@@ -33,6 +30,7 @@ pub struct PreparationServiceBuilder<T: SlotClock + 'static, E: EthSpec> {
     beacon_nodes: Option<Arc<BeaconNodeFallback<T, E>>>,
     context: Option<RuntimeContext<E>>,
     builder_registration_timestamp_override: Option<u64>,
+    validator_registration_batch_size: Option<usize>,
 }
 
 impl<T: SlotClock + 'static, E: EthSpec> PreparationServiceBuilder<T, E> {
@@ -43,6 +41,7 @@ impl<T: SlotClock + 'static, E: EthSpec> PreparationServiceBuilder<T, E> {
             beacon_nodes: None,
             context: None,
             builder_registration_timestamp_override: None,
+            validator_registration_batch_size: None,
         }
     }
 
@@ -74,6 +73,14 @@ impl<T: SlotClock + 'static, E: EthSpec> PreparationServiceBuilder<T, E> {
         self
     }
 
+    pub fn validator_registration_batch_size(
+        mut self,
+        validator_registration_batch_size: usize,
+    ) -> Self {
+        self.validator_registration_batch_size = Some(validator_registration_batch_size);
+        self
+    }
+
     pub fn build(self) -> Result<PreparationService<T, E>, String> {
         Ok(PreparationService {
             inner: Arc::new(Inner {
@@ -91,6 +98,9 @@ impl<T: SlotClock + 'static, E: EthSpec> PreparationServiceBuilder<T, E> {
                     .ok_or("Cannot build PreparationService without runtime_context")?,
                 builder_registration_timestamp_override: self
                     .builder_registration_timestamp_override,
+                validator_registration_batch_size: self.validator_registration_batch_size.ok_or(
+                    "Cannot build PreparationService without validator_registration_batch_size",
+                )?,
                 validator_registration_cache: RwLock::new(HashMap::new()),
             }),
         })
@@ -107,6 +117,7 @@ pub struct Inner<T, E: EthSpec> {
     // Used to track unpublished validator registration changes.
     validator_registration_cache:
         RwLock<HashMap<ValidatorRegistrationKey, SignedValidatorRegistrationData>>,
+    validator_registration_batch_size: usize,
 }
 
 #[derive(Hash, Eq, PartialEq, Debug, Clone)]
@@ -447,7 +458,7 @@ impl<T: SlotClock + 'static, E: EthSpec> PreparationService<T, E> {
         }
 
         if !signed.is_empty() {
-            for batch in signed.chunks(VALIDATOR_REGISTRATION_BATCH_SIZE) {
+            for batch in signed.chunks(self.validator_registration_batch_size) {
                 match self
                     .beacon_nodes
                     .first_success(
@@ -462,7 +473,7 @@ impl<T: SlotClock + 'static, E: EthSpec> PreparationService<T, E> {
                     Ok(()) => info!(
                         log,
                         "Published validator registrations to the builder network";
-                        "count" => registration_data_len,
+                        "count" => batch.len(),
                     ),
                     Err(e) => warn!(
                         log,