diff --git a/defaults/main.yml b/defaults/main.yml
index 98df3d7..f7ef957 100644
--- a/defaults/main.yml
+++ b/defaults/main.yml
@@ -81,6 +81,7 @@ mongodb_cluster_enabled: False
 mongodb_authorization_enabled: False
 mongodb_replicaset: storagedev
 mongodb_replica_keyfile: '{{ mongodb_dbpath }}/replica_keyfile'
+mongodb_oplog_size: 2000
 
 # Prometheus metrics
 mongodb_prometheus_exporter_enabled: False
diff --git a/templates/mongod-3.6.conf.j2 b/templates/mongod-3.6.conf.j2
index b7df6c1..90e8536 100644
--- a/templates/mongod-3.6.conf.j2
+++ b/templates/mongod-3.6.conf.j2
@@ -44,7 +44,7 @@ security:
   keyFile: {{ mongodb_replica_keyfile }}
 
 replication:
-  oplogSizeMB: 2000
+  oplogSizeMB: {{ mongodb_oplog_size }}
   replSetName: {{ mongodb_replicaset }}
   enableMajorityReadConcern: false
 {% endif %}