The 'Glee' actress - who plays Rachel Berry in the US musical drama series - admits she always chooses gowns created by the legendary designer.
She said: "Who's my favourite designer? Oscar de la Renta, of course! I've worn some beautiful Oscar de la Renta dresses over the last few months - at the Golden Globes and the Emmys. I felt like a princess."
The brunette beauty also admitted her fashion sense is nothing like her 'Glee' character's, but she does take inspiration from her mother's wardrobe.
She added to new! magazine: "I don't dress like Rachel. We do have some similar personality traits, but not the same style.
"My mum has great style. I always followed her lead. We share a lot of clothes because we're the same size."
Lea also admitted she hates the gym but keeps active with various forms of outdoor exercise.
She said: "Well, 'Glee in itself' is a great workout, but I also like to do yoga and I get out on my bike. I like to be outside rather than in the gym as much as I can."