Oscillatory activity in the beta frequency range accompanies the formation of long-term memories. Beta power decreases have frequently been shown to correlate with memory formation. However, the causal relationship between beta desynchronization and episodic memory encoding remains unclear. This thesis investigates the causal role beta oscillations play in memory formation and explores ways in which non-invasive brain stimulation can be used to test these causal mechanisms. More specifically, this thesis investigates whether increasing beta power impairs memory formation and whether decreasing beta power improves memory. We used two different non-invasive brain stimulation techniques: tACS was used to increase beta power and impair memory formation, while rTMS was used as a means of decreasing beta power and enhancing memory performance. Chapters 2 and 3 indicate that transient beta tACS does not modulate beta oscillations and does not impair memory formation, while slow rTMS effectively enhanced memory formation by modulating beta power in remote areas, in Chapter 4. This thesis emphasises that negative results are not only important, but necessary to advance our understanding of how non-invasive brain stimulation can help us unravel the causal role that beta oscillatory activity plays in the formation of episodic memories.