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My guess is that your pellet grill has much better heat control and heats much more evenly than your oven. 

Depending on how well your electric oven's thermostat works, the temperature inside the oven can vary wildly or might be very different from the temperature you set. If the oven temperature varies from 300F to 500F during cooking, that could dry meat out and result in a combination of burnt and undercooked. I would use a probe type thermometer to measure how accurate the oven's setting is and how well it holds that temperature over time.

I like Thermoworks and they make 'air' probes that are intended to measure oven and smoker temperatures; a 'penetration' or contact probe intended to measure meat temperatures would not work for this purpose. Different appliance manufacturers have different calibration procedures, but you may be able to fix an inaccurate oven temperature yourself. If the temperature fluctuates a lot, you may have to replace parts to fix it. 

Also, even a little smoke flavor can augment your marinades much like a touch of salt, vanilla or msg can bring out other flavors without you noticing that specific flavor. My mom always kept a bottle of liquid smoke in her pantry for certain recipes.